U.S. patent application number 11/447981 was filed with the patent office on 2007-03-01 for method and apparatus for writing servo information.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Masafumi Iwashiro, Shinichirou Kouhara, Seiji Mizukoshi, Shouji Nakajima, Hideo Sado, Masahide Yatsu.
Application Number | 20070047132 11/447981 |
Document ID | / |
Family ID | 37803733 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070047132 |
Kind Code |
A1 |
Sado; Hideo ; et
al. |
March 1, 2007 |
Method and apparatus for writing servo information
Abstract
According to one embodiment, a servo write method for writing
servo information to a disk medium used in a disk drive is
disclosed. In the procedure of the servo write method, first servo
information is spirally written to a disk medium in a clean room
before the disk medium is incorporated into the disk drive, then,
the disk medium is incorporated into the disk drive, and second
servo information is concentrically written to the disk medium
already incorporated in the disk drive.
Inventors: |
Sado; Hideo; (Ome-shi,
JP) ; Yatsu; Masahide; (Akishima-shi, JP) ;
Iwashiro; Masafumi; (Ome-shi, JP) ; Nakajima;
Shouji; (Kodaira-shi, JP) ; Mizukoshi; Seiji;
(Nishitama-gun, JP) ; Kouhara; Shinichirou;
(Hino-shi, JP) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
37803733 |
Appl. No.: |
11/447981 |
Filed: |
June 7, 2006 |
Current U.S.
Class: |
360/77.01 ;
G9B/5.225 |
Current CPC
Class: |
G11B 5/59655
20130101 |
Class at
Publication: |
360/077.01 |
International
Class: |
G11B 5/58 20060101
G11B005/58 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2005 |
JP |
2005-251039 |
Claims
1. A method, for use in a disk drive into which a head and a disk
medium are incorporated, for writing, to the disk medium, servo
information used to achieve positioning control of the head, the
method comprising: writing, to an entire surface of the disk
medium, first servo information including a plurality of sectors
arranged at regular intervals in a circumferential direction of the
disk medium, the first servo information defining a spiral track;
and writing second servo information to the disk medium with the
first servo information written thereon, based on the first servo
information, the second servo information including a plurality of
sectors arranged at regular intervals in the circumferential
direction of the disk medium, the second servo information defining
concentric tracks.
2. The method according to claim 1, wherein in the writing the
first servo information, the first servo information is written to
the disk medium using a dedicated servo information writing unit,
before the disk medium is incorporated into the disk drive.
3. The method according to claim 1, wherein in the writing the
second servo information, the second servo information is written
to the disk medium using the head incorporated in the disk drive,
after the disk medium with the first servo information written
thereon is incorporated into the disk drive.
4. The method according to claim 1, wherein the writing the second
servo information includes: reading the first servo information
from the disk medium, using the head; executing position correction
computation for correcting head position information computed from
the first servo information read by the head, based on imaginary
concentric tracks corresponding to the concentric tracks; executing
head positioning control based on the head position information
corrected by the position correction computation; and writing the
second servo information to positions determined by the head
positioning control.
5. The method according to claim 4, wherein in the executing the
position correction computation, the position correction
computation is executed based on the imaginary concentric tracks,
using a preset computation expression or preset table
information.
6. The method according to claim 1, wherein in the writing the
second servo information, the second servo information is written
to the disk medium in the defined concentric tracks with a
designated track pitch.
7. The method according to claim 1, wherein the first or second
servo information contains identification information.
8. A disk drive comprising: a head; a disk medium with first servo
information recorded thereon, the first servo information being
used for head positioning control and including a plurality of
sectors arranged at regular intervals in a circumferential
direction of the disk medium, the first servo information defining
a spiral track; a spindle motor which rotates the disk medium; an
actuator which moves the head; a head positioning control unit
which controls the actuator to execute the head positioning control
based on the first servo information read by the head; and a servo
write unit which writes second servo information to the disk medium
to define concentric tracks, while the head is moved by the head
positioning control unit, the second servo information including a
plurality of sectors arranged at regular intervals in the
circumferential direction.
9. The disk drive according to claim 8, wherein the head
positioning control unit executes position correction computation
for correcting head position information computed from the first
servo information read by the head, based on imaginary concentric
tracks corresponding to the concentric tracks, and executes the
head positioning control based on the head position information
corrected by the position correction computation.
10. The disk drive according to claim 8, wherein the head
positioning control unit and the servo write unit are formed of a
microprocessor.
11. The disk drive according to claim 9, wherein the head
positioning control unit is formed of a microprocessor which
executes the position correction computation, and executes the head
positioning control based on the head position information
corrected by the position correction computation.
12. The disk drive according to claim 8, wherein: the head
positioning control unit and the servo write unit are formed of a
microprocessor; the first or second servo information contains
identification information; and the microprocessor identifies the
second servo information read by the head from the disk medium
which records both the first servo information and the second servo
information, and executes the head positioning control based on the
second servo information read by the head, when user data is
written to or read from the disk medium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2005-251039, filed
Aug. 31, 2005, the entire contents of which are incorporated herein
by reference.
BACKGROUND
[0002] 1. Field
[0003] One embodiment of the invention relates to a servo write
method for writing servo information to a disk medium incorporated
in a disk drive, and more particularly to a self-type servo write
method.
[0004] 2. Description of the Related Art
[0005] In general, in disk drives represented by hard disk drives,
servo information used for head-positioning control is recorded on
a disk medium as a data recording medium. Using servo information
read by a head, the head is positioned to a target position (target
track) on the disk medium.
[0006] At the target position to which the head is positioned, the
head writes or reads data. In general, the head includes a read
head element and write head element, and reads data (including
servo information) using the read head element and write data using
the write head element.
[0007] The disk-drive-manufacturing process includes a servo write
process (servo track write process) for recording servo information
on a disk medium. The servo write process performed in a clean room
mainly employs two methods--a write method for writing servo
information to a disk medium using a dedicated servo information
write apparatus (servo track writer), and a self-type servo write
method for writing servo information to a disk medium incorporated
into a disk drive, using the disk drive. In recent years, the
self-type servo write method, which is superior in the accuracy of
servo information, has been widespread.
[0008] In the self-type servo write method, a method has been
proposed in which base servo information is recorded on a disk
medium before the medium is incorporated into a disk drive, and new
servo information is written based on the base servo information,
after the medium is incorporated into the disk drive (see, for
example, Jpn. pat. Appln. KOKAI Publication No. 2005-25826). The
base servo information is written to the disk medium by a servo
track writer in a clean room, before the medium is incorporated
into the disk drive.
[0009] Another method has been proposed in which a spirally
written, patterned medium is prepared, and servo information is
spirally written to a disk medium based on the patterned medium
(see, for example, Jpn. pat. Appln. KOKAI Publication No.
11-45528).
[0010] In the disk-drive-manufacturing process, the time required
for the servo write process for recording servo information is a
factor of reducing the efficiency of the entire manufacturing
process. In particular, in order to enhance the efficiency of the
servo write process, it is important to shorten the time required
to write servo data using a servo track writer in a clean room.
[0011] In disk drives, in general, servo information is recorded
concentrically on a disk medium. Compared to the concentrically
recorded servo information, spirally recorded servo information
employed in the above-mentioned method can be written to the entire
surface of a disk medium in a shorter time, since it requires no
head stop time.
[0012] However, in disk drives on the market, when user data
(computer data, or stream data such as video data) is written to
concentric data tracks on a disk medium, using a head, it is
necessary for the head to read servo information when it is on a
target track, and to be accurately positioned. Namely, in disk
drives in which data is recorded on concentric data tracks on a
disk medium, the servo information recorded on the disk medium must
be concentrically written servo information. In other words, in the
case of using spirally written servo information, the head
positioning accuracy is relatively reduced.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0013] A general architecture that implements the various feature
of the invention will now be described with reference to the
drawings. The drawings and the associated descriptions are provided
to illustrate embodiments of the invention and not to limit the
scope of the invention.
[0014] FIG. 1 is a block diagram illustrating a disk drive
according to an embodiment of the invention;
[0015] FIGS. 2A and 2B are views useful in explaining the features
of first and second servo information items employed in the
embodiment;
[0016] FIG. 3 is a view illustrating each sector data item
contained in the first and second servo information items of the
embodiment;
[0017] FIGS. 4A and 4B are developments corresponding to FIGS. 2A
and 2B, respectively;
[0018] FIG. 5 is a flowchart useful in explaining the procedure of
a servo write method employed in the embodiment;
[0019] FIG. 6 is a flowchart useful in explaining the procedure of
writing first servo information employed in the embodiment;
[0020] FIG. 7 is a view useful in explaining a method for writing
first servo information employed in the embodiment;
[0021] FIGS. 8A and 8B are views useful in explaining a method for
writing second servo information employed in the embodiment;
[0022] FIG. 9 is a flowchart useful in explaining the procedure of
writing second servo information employed in the embodiment;
and
[0023] FIG. 10 is a graph useful in explaining an amount of
correction for positional information performed when the second
servo information is written.
DETAILED DESCRIPTION
[0024] Various embodiments according to the invention will be
described hereinafter with reference to the accompanying drawings.
In general, according to one embodiment of the invention, the servo
write method is used, in a disk drive into which a head and a disk
medium are incorporated, for writing, to the disk medium, servo
information used to achieve positioning control of the head. The
method comprises: writing, to an entire surface of the disk medium,
first servo information including a plurality of sectors arranged
at regular intervals in a circumferential direction of the disk
medium, the first servo information defining a spiral track; and
writing second servo information to the disk medium with the first
servo information written thereon, based on the first servo
information, the second servo information including a plurality of
sectors arranged at regular intervals in the circumferential
direction of the disk medium, the second servo information defining
concentric tracks.
[0025] [Configuration of Disk Drive]
[0026] FIG. 1 is a block diagram illustrating a disk drive 10
according to the embodiment of the invention.
[0027] The disk drive 10 of the embodiment is a hard disk drive
using a disk medium 11 as a magnetic recording medium. First servo
information is spirally written to the disk medium 11, using a
servo track writer, before the disk medium 11 is incorporated into
the disk drive 10. The disk medium 11 with the first servo
information is incorporated into the disk drive 10, secured to a
spindle motor (SPM) 13 to be spun at high speed.
[0028] The disk drive 10 comprises a head 12 including a read head
element for reading data (servo information and user data) from the
disk medium 11, and a write head element for writing data to the
medium 11. Hereinafter, the read and write head elements may be
referred to simply as the head 12. The head 12 is mounted on an
actuator 14 driven by a voice coil motor (VCM) 15.
[0029] The VCM 15 is powered by a driving current supplied from a
VCM driver 21. The actuator 14 is a head moving mechanism
controlled by a microprocessor (CPU) 19, described later, for
positioning the head 12 at a target position (target track) on the
disk medium 11.
[0030] In addition to the above-mentioned head/disk assembly, the
disk drive 10 comprises a pre-amplifier circuit 16, signal
processing unit 17, disk controller (HDC) 18, CPU 19 and memory
20.
[0031] The pre-amplifier circuit 16 includes a read amplifier for
amplifying a read data signal output from the read head
incorporated in the head 12, and a write amplifier for supplying a
write data signal to the write head of the head 12. Namely, the
write amplifier converts, into a write current signal, the write
data signal output from the signal processing unit 17, and supplies
it to the write head.
[0032] The signal processing unit 17 is a circuit for performing
various types of signal processing, and is also called a read/write
channel.
[0033] The HDC 18 functions as an interface between the drive 10
and a host system 22 (e.g., a personal computer or digital device).
More specifically, the HDC 18 controls the transfer of read/write
data between the disk 11 and host system 22.
[0034] The CPU 19 is a main controller in the drive 10, and
controls a self-type servo write operation according to the
embodiment, and standard user-data read/write operations performed
after the disk drive 10 is manufactured. The memory 20 includes a
RAM, ROM, etc., as well as a flash memory (EEPROM) as a nonvolatile
memory, and stores various data and programs necessary for the CPU
19 to perform various types of control.
[0035] (Servo Write Process)
[0036] Referring mainly to the flowcharts of FIGS. 5, 6 and 9, a
description will be given of the procedure of a servo write method
for writing servo information to the disk medium 11.
[0037] Firstly, the entire procedure of the servo write operation
will be described referring to the flowchart of FIG. 5.
[0038] Before incorporating the disk medium 11 into the disk drive
10, the medium 11 is sent to a clean room. In the clean room, first
servo information (spirally written servo information) is written
to substantially the entire surface of the disk medium 11, using a
servo track writer (step S1). Subsequently, the disk medium 11 with
the first servo information is attached to the spindle motor 13 of
the disk drive 10 in the assembly process of the disk drive 10
(step S2).
[0039] In the assembly process of the disk drive 10, the circuits
such as the head 12 and CPU 19, other than the disk medium 11, are
firstly assembled. After that, second servo information
(concentrically written servo information) is written to the disk
medium 11 (step S3). More specifically, the CPU 19 of the disk
drive 10 activates a servo-write-execution program stored in the
memory 20, thereby executing the processing of writing the second
servo information to the disk medium 11.
[0040] When writing the first servo information to the disk medium
11, a dedicated servo information write device of a magnetic
transfer system may be used instead of the servo track writer.
Further, the first servo information may be written to the disk
medium 11 in the clean room, using a pushpin-type servo track
writer, after the medium 11 is incorporated into the disk drive 10.
The pushpin-type servo track writer operates the head 12 in the
disk drive 10 to write the first servo information to the disk
medium 11.
[0041] Referring then to the flowcharts of FIGS. 6 and 9, and FIGS.
2 to 4, 7 and 8, the writing procedure of each of the first and
second servo information items will be described.
[0042] The features of the first and second servo information items
will firstly be described, referring to FIGS. 2A and 2B.
[0043] As shown in FIG. 2A, the first servo information is written
to the disk surface to define a so-called spiral track thereon. In
contrast, as shown in FIG. 2B, the second servo information is
written to the disk surface to define concentric tracks
thereon.
[0044] Both the first and second servo information items are sector
servo information items that each have such a servo pattern as
shown in FIG. 3, in which servo data is written to each sector
(servo sector) arranged at regular intervals in the circumferential
direction of the disk medium 11.
[0045] Specifically, the first servo information comprises servo
data recorded in a plurality of servo sectors 100 included in the
spiral track 110, as shown in FIG. 2A. Similarly, the second servo
information comprises servo data recorded in a plurality of servo
sectors 200 included in each of the concentric tracks 210, as shown
in FIG. 2B.
[0046] As shown in FIG. 3, the servo data recorded in each servo
sector 100, 200 is, for example, amplitude-detection-type servo
pattern data, which comprises a pad (PAD) section 30, servo mark
(SM) section 31, sector section 32, address section 33 and servo
burst pattern section 34. In FIG. 3, reference symbol TC denotes
the track center. Reference symbol W denotes half the track width,
and corresponds to the forward amount of the head 12 advanced while
the disk medium 11 is rotated by one rotation (through 360 degrees)
during the writing of the first servo information.
[0047] The pad section 30 includes a synchronization signal region
called a gap and servo AGC. The servo mark section 31 is a signal
region for identifying the servo sector. The sector section 32 is a
record region that stores a sector code for identifying the
position of the servo sector on the disk medium 11. The address
section 33 is a record region that stores a track code (cylinder
code) indicating the track (cylinder) of the servo sector. The
servo burst pattern section 34 stores burst signals A to D used to
detect the position of the head 12 in the track.
[0048] In the embodiment, the servo mark section 31, for example,
stores information for identifying the first and second servo
information items. When the head 12 reads servo information from
the disk medium 11, the CPU 19 determines, from the servo mark
section 31 included in the read servo information, whether the read
servo information is the first or second servo information.
[0049] FIGS. 4A and 4B are developments of FIGS. 2A and 2B,
respectively.
[0050] In the first servo information, if track center TC positions
between pairs of adjacent servo sectors 100 are connected, a spiral
locus is acquired as shown in FIG. 4A. In contrast, in the second
servo information, if the positions of the track center TC between
pairs of adjacent servo sectors 200 are connected, concentric
tracks are acquired as shown in FIG. 4B.
[0051] (Write Procedure of First Servo Information)
[0052] Referring to FIGS. 6 and 7, the write procedure of the first
servo information will be described.
[0053] As described above, in the embodiment, the first servo
information is written to the entire surface of the disk medium 11
in a clean room, using the servo track writer. At this time, the
servo track writer moves the write head to the outer periphery of
the disk medium 11, and writes first servo information 100 while
moving the head radially inwardly (steps S11 and S12).
[0054] If the servo track writer writes the first servo information
to the disk medium 11 before the medium 11 is incorporated into the
disk drive 10, it uses a dedicated write head. In contrast, if the
servo track writer writes the first servo information in a clean
room to the disk medium 11 incorporated in the disk drive 10, it
operates the head 12 of the disk drive 10 as shown in FIG. 7.
[0055] In any case, the servo track writer writes the first servo
information to the entire surface of the disk medium 11 to define
the spiral track 110 thereon, while controlling the head so as to
move the rotary actuator with the head mounted thereon through
angle .theta. per unit time. FIG. 7 shows the case where the servo
track writer writes the first servo information 100 using the disk
drive 10, while controlling the movement of the head 12 so as to
move the rotary actuator with the head mounted thereon through
angle .theta. per unit time. This head movement control enables the
angular velocity of the rotary actuator 14 to be kept constant
during writing, whereby the first servo information can be written
with high writing accuracy.
[0056] The servo track writer writes the first servo information up
to the innermost surface portion of the disk medium 11, without
stopping the movement of the write head (e.g., the head 12) (step
S13). After finishing the write operation (Yes at step S13), the
servo track writer stops the movement of the write head (step
S14).
[0057] As described above, in the embodiment, when the first servo
information is written to the disk medium 11 in a clean room, the
servo information write operation is performed to define the spiral
track 110. This write method can significantly reduce the time
required for writing, compared to the conventional servo
information write operation performed to define concentric
tracks.
[0058] More specifically, in the servo information write operation
performed to define concentric tracks, it is necessary to stop the
head at a preset radial position on the disk medium 11. Namely, the
movement (seeking operation) of the head, the stop of the movement
of the head, and the write operation by the head are iterated for
defining the tracks. The operation performed to stop the movement
of the head is a factor that increases the time required to write
servo information.
[0059] In contrast, in the first servo information write method
employed in the embodiment to define the spiral track 110, writing
is performed with the head kept moving, to define a spiral, i.e.,
continuous track, as is shown in FIG. 2A. As a result, the servo
information write time can be reduced by the time for which the
head is stopped during the write process.
[0060] (Write Procedure of Second Servo Information)
[0061] Referring then to FIGS. 8 and 9, the write procedure of the
second servo information will be described.
[0062] As described above, in the servo write method of the
embodiment, the disk drive 10 writes the second servo information
to the disk medium 11 with the first servo information 100 already
recorded thereon in a clean room. The write control operation of
the CPU 19 of the disk drive 10 will now be described. The servo
data (see FIG. 3) necessary for the writing of the second servo
information is generally supplied from a host system (computer) 22
connected to the HDC 18 of the disk drive 10.
[0063] Firstly, the CPU 19 moves the head 12 to, for example, the
innermost portion of the disk medium 11 to read the first servo
information 100 using the read head element of the head 12 (step
S21). Based on the read first servo information 100, the CPU 19
executes position computation to compute the position of the head
12. More specifically, the track address and servo burst pattern (A
to D) contained in the first servo information are reproduced by
the signal processing circuit 17 and then supplied to the CPU 19.
The CPU 19 detects the track position from the track address, and
detects the head position in the track range from the servo burst
pattern (A to D).
[0064] As mentioned, the first servo information 100 corresponds to
the spiral track 110. On the other hand, the CPU 19 writes, to the
disk medium 11, second servo information 200 corresponding to the
concentric tracks 210. To this end, the CPU 19 executes position
correction computation for correcting the position information,
acquired from the first servo information 100, based on preset
imaginary concentric tracks (200) (step S22). The CPU 19 executes
the position correction computation, referring to a preset
expression for computation or position correction table information
prestored in the memory 20.
[0065] FIG. 10 shows a correction amount corresponding to each
servo sector and used for the position correction computation (step
S22). The first servo information is written so that the track
center position TC is displaced by half the track width
(corresponding to W in FIG. 3) each time the disk medium 11 is
rotated through 360 degrees. Accordingly, assuming that N servo
sectors are written by the disk drive 10, it is sufficient if when
the servo sector number is 0, the amount of correction is set to 0,
and when the servo sector number is N-1, the amount of correction
is set to W(N-1)/N. The amount of correction may be determined
referring to position correction table information corresponding to
FIG. 10, or using a correction expression that indicates the
characteristic of FIG. 10.
[0066] Specifically, the amount x of correction can be acquired
using equation x=W.times.k/N (k indicates the servo sector number).
In any method, the amount of correction can be determined by
reading sector information 32 contained in a servo pattern. The
position correction computation is actually the operation of
subtracting the amount of correction from the position information
acquired at step S21.
[0067] The CPU 19 iterates the above-described write operations
while moving the head 12 from the innermost portion of the disk
medium 11 to the outermost portion (step S26). The CPU 19 writes
the second servo information while stopping the head 12 each time
the head 12 reaches a preset radial position on the disk medium 11.
As a result, the second servo information is written to define
concentric tracks 210 on the entire surface of the disk medium 11
as shown in FIG. 2B.
[0068] FIGS. 8A and 8B are views illustrating the positioning loci
of the write head assumed when writing the second servo information
200.
[0069] When servo information is written with the same track pitch
(width) as the first servo information, the write head is made to
assume the locus PC shown in FIG. 8A, thereby writing the second
servo information 200 that defines concentric tracks of a single
pitch.
[0070] On the other hand, when servo information is written with
different track pitches, the write head is made to assume the locus
PC shown in FIG. 8B, thereby writing the second servo information
200 that defines concentric tracks of different pitches. Namely,
where a data track (track range except for servo sectors)
corresponding to, for example, 10 tracks is defined on the disk
medium 11 by the already written first servo information, the CPU
19 can define, for example, 20 data tracks by writing the second
servo information 200 that defines concentric tracks with the track
pitch adjusted. In this case, since the first servo information 100
is written by moving the actuator at a constant angular velocity as
shown in FIG. 7, it is written at regular intervals in the radial
direction on the disk medium 11.
[0071] Since the first circuit of the positioning locus PC always
covers the track center TC of the first servo information and a
track portion off the track center TC, first servo information of
the same characteristic can be acquired when the second servo
information is written, regardless of whether the second servo
information is written with a single track pitch or different track
pitches. Also for this reason, it is preferable to make the first
servo information define a spiral track, when the second servo
information is written with different track pitches.
[0072] As described above, in the servo write method of the
embodiment, the first servo information is written to the disk
medium 11 in a clean room to define the spiral track 110, therefore
the time required for writing can be significantly reduced.
[0073] In addition, in the disk drive 10, the second servo
information 200 for defining concentric tracks 210 can be reliably
written to the disk medium 11 by positioning the head 12 based on
the first servo information 100.
[0074] Accordingly, in the shipped disk drive 10, when user data is
written to the concentric data tracks on the disk medium 11, head
positioning control can be executed based on the second servo
information 200 defining the concentric tracks. That is, when user
data is written, the head 12, which is on a target track, reads the
second servo information 200 for the execution of positioning
control. As a result, highly accurate head positioning is realized.
In contrast, if the first servo information 100 defining the spiral
track is used to perform head positioning control on concentric
data tracks, head positioning control will be executed while the
head is not on a target track.
[0075] An erasure process may be provided for erasing the first
servo information 100 from the disk medium 11 after the second
servo information 200 is written. Alternatively, since the CPU 19
executes head positioning control based on the second servo
information when user data is read or written, using information
for discriminating the first and second servo information items
from each other, the first and second servo information may be kept
recorded on the disk medium 11. In this case, when user data is
written, part of the first servo information may be erased by
overwriting.
[0076] In conclusion, in the embodiment, first servo information
defining a spiral track is written to a disk medium in, for
example, a clean room, therefore the time required for writing
servo data can be relatively reduced. Furthermore, since second
servo information defining concentric data tracks is written to the
disk medium to be incorporated into a disk drive, highly accurate
head positioning control can be realized.
[0077] While certain embodiments of the inventions have been
described, these embodiments have been presented by way of example
only, and are not intended to limit the scope of the inventions.
Indeed, the novel methods and systems described herein may be
embodied in a variety of other forms; furthermore, various
omissions, substitutions and changes in the form of the methods and
systems described herein may be made without departing from the
spirit of the inventions. The accompanying claims and their
equivalents are intended to cover such forms or modifications as
would fall within the scope and spirit of the inventions.
* * * * *